Short Term Fuel Trim question

hey Andre im getting my radiator today and im finally able to get the car tuned on partial throttle and idle. im thinking im going to leave the car in open loop and just fine tune the whole map in 250 increments. will i be able to get at least ok gas mileage if i really fine tune all the individual cells? or should i enable closed loop once im done tuning wide open throttle? i really didnt fully understand the course for closed loop and open loop. ive tried plenty of times to ask questions on the forums but i still get no feedback and its been almost a month now. im just really excited to finally get my car going but i dont want to set it on open loop and damage anything in the long run. i got a guy who swears by open loop tuning and he just leaves it on 24/7 but im building a daily comfortable driver i think open loop is ikay for track use but i dont think itg will benefit me for daily commuting. but again please let me know what you think and if you can help me with any advice

It's not a straight forward question that you are trying to get an answer to.

Depending on whether it is a reflash on a mildly modified or heavily modified engine, or it is a stand alone ECU can have an influence on that answer. The accuracy of your sensor calibrations and injector data can greatly influence the accuracy of the open loop fuelling. Your ability with your ECU to accommodate fuelling changes for coolant temp, air temps, etc will how heavily your ECU would need to use closed loop fuelling to maintain target lambda.

You will also find that having a table with load sites every 250rpm in many areas will be largely unnecessary, and the will be points of the map that are hard to tune (such as high rpm low manifold pressure, as they are often only reached entering overrun or lifting off the throttle)

As covered in the courses, for daily commuting, you will spend most of your time in certain areas of the map. Based on your normal gear selection etc, you may find most of your cruise speeds are 3000rpm and below, and sub 100kpa (if a manifold pressure based fuel table).

If your ECU has the ability to utilise closed loop, there aren't many reasons for a street car to not use it, provided sensible trim limits are implemented. Fault detection logic for the wideband sensor that allows the closed loop to be disabled if a sensor fails is a very desirable feature, rather than getting stranded as a faulty sensor is causing the ECU to trim the fuelling too much either way (this ties in with trim limit logic). Many ECU's such as Haltech also store the short term fuel trim in a table to allow you apply it to your tune if you choose, allowing you to refine the tune over time.